It's not that cells can't go awry, it's that perfectly healthy, otherwise identical, cells do not behave predictably to identical stimuli, even on average. That's their normal mode of existence. Some of those behaviors are pathological (eg cancer) but mostly they're not.

Computers don't behave this way at all: you can be reliably sure that if two computers produce different results with the same input that one of them is wrong. If it's a stochastic algorithm at least the averages should be within a certain bound. You can't make the same conclusion with cells.